Many small electronic components are mounted on Printed Circuit Boards (PCB) using surface mount technology (SMT). These SMT components are placed on the appropriate location on the PCB and are subsequently soldered to the PCB by known processes. In order to determine the likelihood of failure of the solder connection between the SMT component and the PCB, it is necessary to perform testing of the solderability of samples of the component.
Current instruments being used for solderability testing essentially include analytical balances with a built-in clock poised over molten solder. The SMT component is suspended from the bottom of the balance prior to testing. The SMT component has flux applied to it and is dipped into the molten solder. The solder may be in a bath or formed as a small globule. The resulting surface tension of the molten solder wetting to the component is measured by the analytical balance over a period of time. The resulting measurements are used to plot a graph of the wetting force (i.e. the surface tension) versus time, which is then used to determine whether the component has suitable wetting properties for providing good solderability. In order for the quality of solderability of the component to be considered adequate, the sample component must wet quickly enough during the time that it is in contact with the molten solder and must exhibit a wetting force large enough to provide a suitably sized solder fillet in the completed solder joint.
Where the testing uses small solder globules, and as available solderability testing instrument pin sizes have decreased from a 4 mm diameter to 1 mm, the limitations of the testing arrangements described above make it difficult to accurately measure the wetting forces of the newest small components. This is in part because of the smaller amounts of solder required for the smaller pins. The sensitivity of the equipment used to measure the wetting forces in such arrangements is inadequate for the smaller wetting forces required to be measured for the smaller SMT pin sizes. Some such arrangements have a smallest full scale division of force measurement in milliNewtons, which is inadequate to measure forces in the order of microNewtons. The newly developed small pin sizes and smaller solder amounts required for such pin sizes means that greater precision in force measurement is needed. However, when measuring such small forces, thermal currents in air at standard pressure may be high enough relative to the small wetting forces that unreliable results would be recorded or the test may be compromised.
Further, arrangements that rely on suspending a sample over molten solder before contacting the solder suffer from non-uniform heating of the component sample. As the heating in a real reflow oven in the normal assembly process is relatively uniform, it is desirable to mimic such conditions during the testing process, if possible. While the above described arrangements can suspend the component sample over the molten solder for a period of time to heat it prior to immersion in the solder, this generally does not result in uniform heating of the component sample.
It is desired to address or ameliorate one or more shortcomings or disadvantages of prior methods and systems for testing the solderability of surface mount components, or to at least provide a useful alternative thereto.